Improved structural stability and ionic conductivity of Na3Zr2Si2PO12 solid electrolyte by rare earth metal substitutions.

Sodium zirconium silicon phosphorus with the composition of Na 3 Zr 2 Si 2 PO 12 (NZSP) was prepared by a facile solid state reaction method. The effects of the calcination temperature and rare earth element substitution on the structure and ionic conductivity of the NZSP material were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and AC impedance measurement. The results show that the microstructure and ionic inductivity of the NZSP was strongly affected by the aliovalent substitution of Zr 4+ ions in NZSP with rare earth metal of La 3+ , Nd 3+ and Y 3+ . At room temperature, the optimum bulk and total ionic conductivity of the pure NZSP solid electrolyte sintered under different conditions were 6.77×10 −4 and 4.56×10 −4 S cm −1 , respectively. Substitution of La 3+ , Nd 3+ and Y 3+ in place of Zr 4+ exhibited higher bulk conductivity compared with that of pure NZSP. Maximum bulk and ionic conductivity value of 1.43×10 −3 and 1.10×10 −3 S cm −1 at room temperature were obtained by Na 3+x Zr 1.9 La 0.1 Si 2 PO 12 sample. The charge imbalance created by aliovalent substitution improves the mobility of Na + ions in the lattice, which leads to increase in the conductivity. AC impedance results indicated that the total ionic conductivity strongly depends on the substitution element and the feature of the grain boundary. [ABSTRACT FROM AUTHOR]